Abstract
Background
Classic spirometry is effort-dependent and of limited value in assessing small airways. Peripheral airway involvement, and relation to poor control, in asthma, has been highlighted recently. Forced oscillation technique (FOT) offers an effort-independent assessment of overall and peripheral lung mechanics. We studied the association between lung function variables, obtained either by spirometry or multi-frequency (5, 11 and 19 Hz) FOT, and asthma diagnosis and control.
Methods
Spirometry measures, resistance at 5 (R5) and 19 Hz (R19), reactance at 5 Hz (X5), resonant frequency (fres), resistance difference between 5-19 Hz (R5-R19) and Asthma Control Test scores were determined in 234 asthmatic and 60 healthy subjects (aged 13-39 years). We used standardised lung function variables in logistic regression analyses, unadjusted and adjusted for age, height, gender, weight.
Results
Lower FEV1/FVC (OR (95% CI) 0.47 (0.32, 0.69)) and FEF50 (0.62 (0.46, 0.85)) per standard deviation increase, and higher R5 (3.31 (1.95, 5.62)) and R19 (2.54 (1.65, 3.91)) were associated with asthma diagnosis. Independent predictive effects of FEV1/FVC and R5 or R19, respectively, were found for asthma diagnosis. Lower FEV1/FVC and altered peripheral FOT measures (X5, fres and R5-R19) were associated with uncontrolled asthma (p-values < 0.05).
Conclusions
Resistance FOT measures were equally informative as spirometry, related to asthma diagnosis, and furthermore, offered additive information to FEV1/FVC, supporting a complementary role for FOT. Asthma control was related to FOT measures of peripheral airways, suggesting a potential use in identifying such involvement. Further studies are needed to determine a clinical value, and relevant reference values in children, for the multi-frequency FOT measurements.
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